WO2015182768A1

WO2015182768A1 - Vacuum heat-insulating material

Info

Publication number: WO2015182768A1
Application number: PCT/JP2015/065647
Authority: WO
Inventors: 伸広篠原; 裕也濱田
Original assignee: 旭硝子株式会社
Priority date: 2014-05-30
Filing date: 2015-05-29
Publication date: 2015-12-03
Also published as: EP3150897A4; EP3150897A1; CN106415107B; KR20170012202A; EP3150897B8; JPWO2015182768A1; CN106415107A; EP3150897B1

Abstract

　Provided is a vacuum heat-insulating material that has sufficient strength and is easily handled. In this vacuum heat-insulating material (1): a compact (10), molded from a powder containing fumed silica and a core containing fibers, is decompressed and sealed inside an airtight outer bag (12); the fiber length (D30) of the fibers is 100 µm or greater; the fiber length (D90) of the fibers is 20 mm or less; the fumed silica content ratio in the powder is 70 mass% or greater; and the fiber content ratio per 100 parts by mass of the total powder mass is 2 to 30 parts by mass.

Description

Vacuum insulation

The present invention relates to a vacuum heat insulating material having sufficient strength and good handleability.

In various fields such as houses, buildings, vehicles, thermal insulation containers, refrigerators, and water heaters, vacuum insulation is used to reduce energy consumption by insulation. As a vacuum heat insulating material, for example, a vacuum heat insulating material in which powder or fiber as a core material is sealed in an outer bag under reduced pressure is known. Although vacuum insulation using powder as the core material is inferior to the initial heat insulation performance compared to vacuum insulation material using fibers as the core material, it is excellent in long-term durability because it can maintain sufficient heat insulation performance even at low vacuum. . Further, when powder is used as the core material, there is an advantage that it is easy to make a thin plate product or a curved product.

However, the core material made of powder has poor workability. In addition, in order to obtain sufficient heat insulation performance, it is necessary to form a molded body with a pressure press at a low density, so it is difficult to obtain a high-strength vacuum heat insulating material. Therefore, a vacuum heat insulating material using both powder and fiber as a core material has been proposed. Specifically, the following vacuum heat insulating materials (1) to (3) can be mentioned.
(1) A vacuum heat insulating material using a molded body in which wet silica and a fiber reinforcing material are mixed and compressed (Patent Document 1).
(2) A vacuum heat insulating material using a molded product obtained by mixing dry silica, wet silica and a fiber reinforcing material and compression molding (Patent Document 2).
(3) A vacuum heat insulating material using a molded body having a density of 100 to 300 kg / m ³ obtained by mixing dry silica, carbon black and an inorganic fiber material, followed by pressure molding (Patent Document 3).

Japanese Patent Publication No. 4-46348 Japanese Patent Publication No. 5-66341 Japanese Patent No. 3482399

However, even with the vacuum heat insulating materials (1) to (3), it is difficult to obtain a sufficient strength, particularly when the molded body is large, and there are cases in which the handling property is insufficient and a failure such as breaking during transportation may occur.

An object of the present invention is to provide a vacuum heat insulating material having sufficient strength and good handling properties.

In the vacuum heat insulating material of the present invention, a molded body in which a powder containing fumed silica and a core material containing fibers are molded is sealed in an airtight outer bag under reduced pressure, and the fiber length D30 of the fibers is 100 μm. The fiber length D90 of the fiber is 20 mm or less, the content ratio of fumed silica in the powder is 70% by mass or more, and the content of the fiber with respect to 100 parts by mass of the total mass of the powder The ratio is 2 to 30 parts by mass.
The vacuum heat insulating material of the present invention is a molded product in which a powder containing fumed silica, a binder, and a fiber-containing core material are molded, and is sealed in an outer bag having airtightness under reduced pressure. D30 is 100 μm or more, and the fiber length D90 of the fiber is 20 mm or less, the content of fumed silica in the powder is 70% by mass or more, and the total mass of the powder with respect to 100 parts by mass The fiber content may be 2 to 30 parts by mass.

In the vacuum heat insulating material of the present invention, the content ratio of the binder with respect to 100 parts by mass of the total mass of the powder is preferably 0.1 to 15 parts by mass.
Moreover, it is preferable that the said powder further contains either one or both of porous silica and a radiation suppression material.
Moreover, it is preferable that the content rate of the said porous silica in the said powder (100 mass%) is 30 mass% or less.
Moreover, it is preferable that the content rate of the said radiation suppression material in powder (100 mass%) is 30 mass% or less.
Further, the core material comprises a binder with fumed silica binder is applied to the surface, and the mass M _B of the mass M _A and the porous silica of the binder applied prior to the fumed silica contained in the powder The ratio (M _A / M _B ) is preferably 70/30 to 100/0.
The density of the molded body is preferably 0.15 to 0.35 g / cm ³ .
Moreover, it is preferable that the said fiber is any one or both of a resin fiber and an inorganic fiber.
The fibers are alumina fiber, mullite fiber, silica fiber, glass wool, glass fiber, rock wool, slag wool, silicon carbide fiber, carbon fiber, silica / alumina fiber, silica / alumina / magnesia fiber, silica / alumina / zirconia. It is preferable to include at least one inorganic fiber selected from the group consisting of fibers and silica / magnesia / calcia fibers.
Moreover, it is preferable that the vacuum degree in the said outer bag is 1 * 10 < ³ > Pa or less.
Moreover, it is preferable that bending strength is 5 kPa or more and bending strength after temporary fracture is 5 kPa or more.

The vacuum heat insulating material of the present invention has characteristics such as sufficient strength and good handling properties even when the molded body is large, and is less likely to break during transportation.

It is the schematic cross section which showed an example of the vacuum heat insulating material of this invention. It is the graph which showed an example of the stress-strain curve in a three-point bending test. It is the graph which showed an example of the stress-strain curve in a three-point bending test. It is the graph which showed an example of the stress-strain curve in a three-point bending test.

The following definitions of terms apply throughout this specification and the claims.
The “core material” means a material for forming a molded body in the vacuum heat insulating material, which is formed into a desired shape by molding.
The “fumed silica with binder” means that a binder has been added to the surface of fumed silica before mixing with other components such as porous silica and fibers. Fumed silica means silica fine particles composed of primary particles that are amorphous and spherical and have no pores. Fumed silica can be obtained, for example, by vaporizing silicon tetrachloride and performing a gas phase reaction in a high-temperature hydrogen flame.
“Radiation suppression material” means that infrared light is reflected (scattered) or isotropically emitted when the infrared light is once absorbed and the temperature rise due to the absorption is re-radiated. This means particles that suppress radiant heat transfer by disturbing the directionality of.
“Fiber length D30” means the fiber length at which the cumulative number becomes 30% in the cumulative number distribution curve where the total number of fiber length distributions obtained on the basis of the number is 100%. “Fiber length D90” means the fiber length at which the cumulative number reaches 90% in the cumulative number distribution curve where the total number of fiber length distributions obtained on the basis of the number is 100%. The fiber length distribution is obtained from a frequency distribution and a cumulative number distribution curve obtained by randomly measuring the length of 50 or more fibers in a photograph observed with an optical microscope.
“Bending strength” means the maximum value of stress in a three-point bending test. Further, the “bending strength after temporary fracture” means the maximum value of stress in a region where the stress continues to gradually decrease as the strain is increased after the strain at which the bending strength is obtained in the three-point bending test. For example, in the case of the stress-strain curve A illustrated in FIG. 2, the stress a (kPa) that is the maximum value of the stress is the bending strength, and the stress in the region A ′ where the stress continues to gradually decrease as the strain is increased thereafter. The maximum value of stress b (kPa) is the bending strength after temporary fracture. In the case of the stress-strain curve B illustrated in FIG. 3, the stress c (kPa) which is the maximum value of the stress is the bending strength, and the maximum value of the stress in the region B ′ where the stress continues to gradually decrease as the strain is increased thereafter. The stress d (kPa) is a bending strength after temporary fracture. In the case of the stress-strain curve C illustrated in FIG. 4, the stress e (kPa) which is the maximum value of the stress is the bending strength, and the maximum value of the stress in the region C ′ where the stress continues to gradually decrease as the strain is increased thereafter. Also, since the stress is e (kPa), the bending strength after the temporary fracture is assumed to coincide with the bending strength.

(Vacuum insulation)
FIG. 1 is a schematic cross-sectional view showing an example of the vacuum heat insulating material of the present invention.
As shown in FIG. 1, the vacuum heat insulating material 1 includes a molded body 10 in which a core material is molded, and an outer bag 12 having airtightness. The vacuum heat insulating material 1 is a heat insulating material in which a molded body 10 is sealed in a vacuum in an outer bag 12.

(Molded body)
The molded body 10 is obtained by molding a core material containing a powder containing fumed silica and fibers. The molded body 10 may be formed by molding a core material including a powder containing fumed silica, a binder, and fibers.

(powder)
The powder includes fumed silica, and may include one or both of porous silica and a radiation suppressing material as other powder, if necessary. The powder may be only fumed silica. Moreover, the other powder used together with fumed silica may be only 1 type, and 2 or more types may be sufficient as it.

Since fumed silica is an extremely fine powder, a specific surface area is usually used as an index representing the particle size.
The specific surface area of the fumed silica is preferably 50 ~ 400m ² / g, more preferably 100 ~ 350m ² / g, particularly preferably 200 ~ 300m ² / g. If the specific surface area of fumed silica is more than the said lower limit, the outstanding heat insulation performance will be easy to be obtained. If the specific surface area of fumed silica is not more than the above upper limit value, it is easy to attach a binder to the surface of the particles.
The specific surface area in the present invention is measured by a nitrogen adsorption method (BET method).

Specific examples of fumed silica include Aerosil 200 (specific surface area 200 m ² / g, manufactured by Nippon Aerosil Co., Ltd.), Aerosil 300 (specific surface area 300 m ² / g, manufactured by Nippon Aerosil Co., Ltd.), CAB-O-SIL M- 5 (specific surface area 200 m ² / g, manufactured by Cabot Japan), CAB-O-SIL H-300 (specific surface area 300 m ² / g, manufactured by Cabot Japan), Leoroseal QS30 (specific surface area 300 m ² / g, manufactured by Tokuyama Corporation) ) And the like.
Fumed silica may use only 1 type and may use 2 or more types together.

The specific surface area of porous silica is preferably 100 ~ 800m ² / g, more preferably 200 ~ 750m ² / g, particularly preferably 300 ~ 700m ² / g. If the specific surface area of the porous silica is equal to or greater than the lower limit, excellent heat insulating performance can be easily obtained. If the specific surface area of the porous silica is not more than the above upper limit, the amount of binder absorbed by the porous silica can be reduced. Therefore, even if there is little binder amount added, a molded object can be shape | molded by a lower pressure, As a result, the density of a molded object can be made low and it becomes easy to obtain the outstanding heat insulation performance.

The porosity of the porous silica is preferably 60 to 90%, more preferably 65 to 85%, and particularly preferably 70 to 80%. If the porosity of the porous silica is equal to or higher than the lower limit, the heat conduction of the solid can be reduced, and thus excellent heat insulating performance can be easily obtained. When the porosity of the porous silica is not more than the above upper limit value, the porous silica particles are hardly crushed during molding, and excellent heat insulating performance is easily obtained because the porosity is maintained. The porosity is measured by a nitrogen adsorption method (BET method).

The average particle diameter of the porous silica is preferably 1 to 300 μm, more preferably 2 to 150 μm, and particularly preferably 3 to 100 μm, when measured on a volume basis by a laser diffraction scattering method or a Coulter counter method. When the average particle diameter of the porous silica is not less than the lower limit, porous silica having a high porosity can be easily obtained, and excellent heat insulating performance can be easily obtained. If the average particle diameter of the porous silica is not more than the above upper limit value, the density of the molded body does not become too high, and excellent heat insulating performance is easily obtained.

Specific examples of porous silica include M.I. S. Examples include GEL and sunsphere (both manufactured by AGC S-Tech). The porous silica may be used alone or in combination of two or more.

When the core material contains a radiation suppression material, infrared light is reflected (scattered) or isotropically emitted when the infrared light is absorbed once and the temperature rise due to the absorption is re-radiated. As a result, the total amount of infrared light passing through the molded body is reduced, so that radiant heat transfer is suppressed. It is preferable that the radiation suppressing material is uniformly dispersed in the core material because contact between the radiation suppressing materials is reduced and a solid heat transfer path is hardly formed.

Examples of the radiation suppressing material include metal particles (aluminum particles, silver particles, gold particles, etc.), inorganic particles (graphite, carbon black, silicon carbide, titanium oxide, tin oxide, potassium titanate, etc.) and the like. Only one type of radiation suppressing material may be used, or two or more types may be used in combination.
The average particle size of the radiation suppressing material is preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm, and particularly preferably 1 to 20 μm. If the average particle diameter of the radiation suppressing material is equal to or greater than the lower limit value, it is easy to uniformly disperse the radiation suppressing agent in the molded body, and it is easy to obtain excellent heat insulation. If the average particle diameter of the radiation suppressing material is not more than the above upper limit value, the strength of the molded body does not become too low, and the molded body is easy to handle.

(Binder)
The core material in the present invention may contain a binder.
By including a binder in the core material, fumed silica or fumed silica and other components (porous silica, fibers, etc.) are bonded to each other and have sufficient strength even when the pressure during molding is low. It becomes a vacuum heat insulating material provided with a molded object.
The binder is preferably applied to fumed silica in advance before mixing other components to form fumed silica with a binder. Thereby, it becomes easy to obtain the effect by a binder sufficiently. Even if the binder is applied to the porous silica, the binder is absorbed by the porous silica, so that it is difficult to obtain the effect of the binder.

The binder may be an organic binder or an inorganic binder. Especially, as a binder, an inorganic binder is preferable from the point that heat conductivity is low and the outstanding heat insulation performance is easy to be obtained.
Examples of the inorganic binder include sodium silicate, aluminum phosphate, magnesium sulfate, magnesium chloride and the like. Among these, sodium silicate is particularly preferable from the viewpoint that excellent heat insulating properties can be easily obtained.
A binder may use only 1 type and may use 2 or more types together.

(fiber)
As a fiber, the fiber normally used for a vacuum heat insulating material can be used, For example, a resin fiber and an inorganic fiber are mentioned. Of these, inorganic fibers are preferred because they are less volatile of gas components under vacuum, can easily suppress a decrease in heat insulation performance due to a decrease in the degree of vacuum, and are excellent in heat resistance. Only 1 type of fiber may be used and 2 or more types may be used together.

Examples of inorganic fibers include alumina fiber, mullite fiber, silica fiber, glass wool, glass fiber, rock wool, slag wool, silicon carbide fiber, carbon fiber, silica / alumina fiber, silica / alumina / magnesia fiber, silica / alumina / Examples thereof include zirconia fiber and silica / magnesia / calcia fiber. Among these, glass fiber, rock wool, or silica / magnesia / calcia fiber is preferable from the viewpoint of price and safety.

The fiber length D30 of the fibers used is 100 μm or more, preferably 200 μm or more, and more preferably 500 μm or more. If fiber length D30 is more than the said lower limit, the high intensity | strength vacuum heat insulating material which is hard to fracture | rupture will be obtained.
The fiber length D90 of the fiber used is 20 mm or less, preferably 10 mm or less, and particularly preferably 5 mm or less. If the fiber length D90 is less than or equal to the above upper limit value, the fibers are not easily entangled, so that they are easily mixed with the powder and the effect of the fibers is sufficiently obtained.
The thickness (diameter) of the fiber is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less from the viewpoint of suppressing an increase in solid heat transfer due to the fiber. Further, the thickness (diameter) of the fiber is preferably 1 μm or more, more preferably 3 μm or more, from the viewpoint that a high-strength vacuum heat insulating material that is difficult to break is easily obtained. The fiber thickness is more preferably 3 to 15 μm.

(Powder, binder, fiber ratio)
The (containing) ratio of fumed silica in the powder (100% by mass) is 70% by mass or more, preferably 70 to 100% by mass, more preferably 80 to 100% by mass, particularly 90 to 100% by mass. preferable. If the ratio of fumed silica is equal to or higher than the lower limit, a high-strength vacuum heat insulating material can be easily obtained.

The proportion (inclusive) of porous silica in the powder (100% by mass) is preferably 30% by mass or less, more preferably 2 to 20% by mass, and particularly preferably 5 to 10% by mass. If the ratio of porous silica is more than the said lower limit, the vacuum heat insulating material excellent in heat insulation performance will be obtained. If the ratio of porous silica is not more than the above upper limit value, it is easy to obtain a vacuum heat insulating material having high strength.

When using a binder with fumed silica to impart a binder in advance surface as a core material, the ratio of the mass M _B of the mass M _A and the porous silica fumed silica before the binder imparting (M A _{/ M} _B) is 70/30 to 100/0 is preferable, 80/20 to 98/2 is more preferable, and 90/10 to 95/5 is particularly preferable. If M A _/ M _B is the range, the molded article having a sufficient strength at a lower density is obtained, the vacuum heat insulating material can be easily obtained with excellent thermal insulation performance.

The content ratio of the radiation suppressing material in the powder (100% by mass) is preferably 30% by mass or less, more preferably 5 to 25% by mass, and particularly preferably 10 to 20% by mass. If the ratio of the radiation suppressing material is equal to or higher than the lower limit value, the effect of the radiation suppressing material is easily obtained. If the ratio of the radiation suppressing material is equal to or less than the above upper limit value, an increase in solid heat transfer due to the radiation suppressing material can be suppressed, and thus excellent heat insulating performance can be easily obtained.

The content ratio of the binder is preferably 0.1 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, and further preferably 1 to 2 parts by mass with respect to 100 parts by mass of the powder. If the ratio of the binder is equal to or higher than the lower limit value, a molded body having a lower density and sufficient strength can be obtained, so that a vacuum heat insulating material excellent in heat insulating performance can be obtained. If the ratio of the said binder is below the said upper limit, since the increase in the solid heat transfer by a binder can be suppressed, the fall of heat insulation performance is suppressed.

The fiber (containing) ratio is 2 to 30 parts by mass, preferably 4 to 20 parts by mass, and more preferably 5 to 10 parts by mass with respect to 100 parts by mass of the powder. When the fiber ratio is equal to or higher than the lower limit, a high-strength vacuum heat insulating material that is difficult to break can be easily obtained. If the ratio of a fiber is below the said upper limit, since the increase in the solid heat transfer by a fiber can be suppressed, it is easy to suppress the fall of heat insulation performance.

The density of the green body 10 is preferably 0.15 ~ 0.35g / cm ^3, more preferably 0.17 ~ 0.21g / cm ^3. If the density of the molded body 10 is equal to or higher than the lower limit value, the molded body is easy to handle, and the powder is less likely to be scattered from the molded body when sealed under reduced pressure. If the density of the molded object 10 is below the said upper limit, the outstanding heat insulation performance will be easy to be obtained stably.

(Outer bag)
The outer bag 12 has only to be airtight and can seal the molded body 10 under reduced pressure. Examples of the outer bag 12 include a bag made of a gas barrier film. As the gas barrier film, a known one used for a vacuum heat insulating material can be used without limitation.
The magnitude | size and shape of the outer bag 12 are not specifically limited, What is necessary is just to determine suitably according to the magnitude | size and shape of the target vacuum heat insulating material 1. FIG.

The vacuum degree in the outer bag 12 in the vacuum heat insulating material 1 is preferably 1 × 10 ³ Pa or less, preferably 5 × 10 ² Pa or less from the viewpoint that excellent heat insulating performance is obtained and the life of the vacuum heat insulating material 1 is prolonged. Is more preferable, and 1 × 10 ² Pa or less is more preferable. The degree of vacuum in the outer bag 12 is preferably 1 Pa or more, and more preferably 10 Pa or more, from the viewpoint of easy decompression of the outer bag.

The bending strength of the vacuum heat insulating material of the present invention is preferably 5 kPa or more, more preferably 10 kPa or more, and further preferably 20 kPa or more. If the bending strength is equal to or higher than the lower limit, it is easy to handle the molded body.

The bending strength after temporary fracture of the vacuum heat insulating material of the present invention is preferably 5 kPa or more, and more preferably 10 kPa or more. If the bending strength after temporary fracture is equal to or higher than the lower limit, handling properties are good.

(Production method)
As a manufacturing method of the vacuum heat insulating material 1, the method of having the following process (x) and process (y) is mentioned, for example.
(X) A step of pressing the powder containing fumed silica, the binder, and the core material containing fibers to obtain the molded body 10.
(Y) A step of obtaining the vacuum heat insulating material 1 by sealing the molded body 10 in the outer bag 12 under reduced pressure.

(Process (x))
After a powder containing fumed silica, a binder, and fibers are mixed to obtain a core material, the core material is pressed and molded to obtain a molded body 10.
Examples of the method of mixing the fumed silica-containing powder, the binder, and the fiber include a method using a V-type mixer, a blender with a stirrer, or the like. Especially, the method of using a high-speed stirring apparatus like a blender with a stirrer is preferable from the point that the dispersibility of each component becomes favorable.

In the step (x), when porous silica is used in combination, it is preferable to give a binder to the fumed silica before mixing with components other than the fumed silica to obtain a fumed silica with a binder. Thereby, since it can suppress that a binder becomes absorbed by porous silica and an effect becomes difficult to be acquired, the usage-amount of a binder can be reduced.
The timing of mixing the binder is not particularly limited. For example, fumed silica, porous silica, fiber, and binder may be mixed at the same time.

The binder is preferably dissolved in a solvent and mixed as a binder solution. It does not specifically limit as a solvent used for a binder liquid, For example, water, ethanol, etc. are mentioned. Of these, water is preferred. By adding water, the fumed silica and the porous silica are prevented from being charged, and the powder hardly adheres to the mold or the like. Moreover, handling of powder becomes easy by improving the fluidity of the powder.
As the binder liquid, water glass which is an aqueous solution of sodium silicate is particularly preferable.

The ratio of the solid content serving as the binder in the binder liquid (100% by mass) is preferably 0.2 to 40% by mass, and more preferably 3 to 10% by mass. When the ratio of the binder is within the above range, it is easy to apply the binder to the powder.
The amount of water added to the core material is preferably 5 to 50 parts by mass and more preferably 10 to 30 parts by mass with respect to 100 parts by mass of the total mass of the powder. If the amount of water added is equal to or greater than the lower limit, the powder is less likely to adhere to the mold or the like, and the powder is easier to handle due to increased fluidity of the powder. If the amount of water added is equal to or less than the above upper limit value, the density of the molded body is easily lowered, and thus a vacuum heat insulating material excellent in heat insulating performance is easily obtained.
The binder liquid may be applied to the powder or fiber by spray coating or the like.

It is preferable that the solvent of the binder liquid mixed with the powder is volatilized before the compact 10 is sealed in the outer bag 12 in the step (y). As a result, the powders and the powders and fibers are better bonded by the binder. Examples of the method of volatilizing the solvent include a method of heating with a constant temperature dryer or an electric furnace.

As a method of obtaining the molded body 10 by molding the core material, a known method can be adopted, and examples thereof include a method of charging the core material into a mold and molding it by pressing.

(Process (y))
For example, after the molded body 10 obtained in the step (x) is stored in the outer bag 12 and the outer bag 12 is sealed under a reduced pressure condition, the outside of the outer bag 12 is returned to the atmospheric pressure condition to obtain a vacuum heat insulating material. Get one. Specifically, the molded body 10 is stored in an outer bag 12 in which two films are overlapped and three sides are sealed in advance, and placed in a vacuum chamber having a heat seal function. Depressurize the inside. After the inside of the chamber is depressurized to a predetermined pressure, the remaining one side of the outer bag 12 is heat-sealed and sealed, and then the inside of the chamber is returned to the atmospheric pressure condition.
In the step (y), after the molded body 10 is stored in the outer bag 12, the outer bag 12 is sealed by heat sealing or the like while sucking out the air in the outer bag 12 to decompress the inside of the outer bag 12. Thus, a method of sealing the molded body 10 in the outer bag 12 under reduced pressure may be employed.

The vacuum heat insulating material of the present invention described above uses a molded body obtained by molding a core material containing a powder containing fumed silica, a binder, and a fiber having a specific fiber length in a specific ratio. It has sufficient strength, has good handling properties, and does not easily cause problems such as breaking during transportation.

In addition, the vacuum heat insulating material of the present invention is not limited to the vacuum heat insulating material 1 described above. For example, the vacuum heat insulating material of the present invention may be a vacuum heat insulating material that is sealed under reduced pressure in an outer bag in a state where a molded body is housed in a breathable inner bag. In other words, a molded body made of a core material stored in an inner bag may be used.

As said inner bag, what is necessary is just what has air permeability and can prevent the powder which forms a core material from leaking at the time of pressure reduction enclosure, for example, the bag etc. which consist of paper materials, a nonwoven fabric, etc. are mentioned. .
The size and shape of the inner bag are not particularly limited, and may be appropriately determined according to the size and shape of the target vacuum heat insulating material.
As a manufacturing method of the vacuum heat insulating material in the case of using the inner bag, the vacuum heat insulating material 1 has been described except that the molded body is housed in the inner bag in step (y) and sealed in the outer bag under reduced pressure. A method similar to the method can be adopted.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by a following example.
[Measurement of fiber length]
The fiber lengths D30 and D90 of the fibers used as the raw material are determined on the basis of the number from the frequency distribution and cumulative number distribution curve by measuring the length of 50 or more fibers randomly extracted from the photograph observed with an optical microscope. It was calculated from the fiber length distribution.

[Measurement of bending strength and bending strength after temporary break]
The bending strength and the bending strength after temporary fracture of the vacuum heat insulating material obtained in each example were measured by performing a three-point bending test with a precision universal testing machine Autograph AGS-J (manufactured by Shimadzu Corporation).
The maximum value of stress in the three-point bending test was defined as the bending strength. Further, the maximum value of the stress in a region where the stress is gradually reduced as the strain is increased after the strain at which the bending strength is obtained is defined as the bending strength after temporary fracture.

[Measurement of thermal conductivity]
The thermal conductivity of the vacuum heat insulating material obtained in each example was measured using a thermal conductivity measuring device HC-110 (manufactured by Eiko Seiki Co., Ltd.).

[Molded density]
The density of the compact was calculated from the dimensions and mass of the compact.
[Handling]
In each step such as drying of the molded body and insertion into a film, the one that did not break even if only one side of the molded body was supported with one hand was judged good, and the one that broke was made insufficient.

[Example 1]
2. Fumed silica (trade name “Aerosil 300”, specific surface area 300 m ² / g, manufactured by Nippon Aerosil Co., Ltd., the same shall apply hereinafter) 40 parts by mass of sodium silicate No. 3 (manufactured by AGC S-Itech Co., Ltd.) A binder solution obtained by diluting 4 parts by mass (1.3 parts by mass in terms of solid content) with 22.9 parts by mass of ion-exchanged water was mixed with a blender. Thereafter, 40 parts by mass of fumed silica and M. S. 20 parts by mass of GEL (manufactured by AGC S-Tech) are added, and silica, magnesia calcia fiber (trade name “Superwool (registered trademark) Plus) bulk” as inorganic fiber, D30: 227 μm, D90: 902 μm, new 2 parts by mass) (manufactured by Nippon Thermal Ceramics Co., Ltd.) was added and mixed with a blender to obtain a core material.

The obtained core material was put into a mold and formed into a flat plate shape having a length of 40 mm, a width of 20 mm and a thickness of 5 mm by applying pressure, and then heated at 200 ° C. for 1 hour to prepare a molded body. The obtained molded body was measured for bending strength and bending strength after temporary fracture. Thereafter, the obtained molded body was put into a commercially available gas barrier film (ADY-134, manufactured by ADW) heat-sealed on only three sides, and placed in a vacuum chamber with a heat-sealing function. Thereafter, the pressure in the chamber was reduced to 30 Pa, and in that state, the opening of the outer bag was heat-sealed and sealed, and the outside of the outer bag was returned to atmospheric pressure conditions to obtain a vacuum heat insulating material.
In addition, after obtaining a molded body having a length of 80 mm × width of 80 mm × thickness of 5 mm using the core material, the molded body was put into a commercially available gas barrier film (ADY-134, manufactured by ADW Corporation) heat-sealed only on three sides. The thermal conductivity was measured in a chamber whose pressure was reduced to 30 Pa. Then, it installed in the vacuum chamber with a heat seal function. The inside of the chamber was decompressed to 30 Pa, and in that state, the opening of the outer bag was sealed by heat sealing, and the outside of the outer bag was returned to atmospheric pressure conditions to obtain a vacuum heat insulating material.

[Examples 2 to 7, 10]
A core material was obtained in the same manner as in Example 1 except that the composition of the core material was changed as shown in Table 1. Thereafter, the bending strength, the bending strength after temporary fracture, the vacuum heat insulating material, and the thermal conductivity of the molded body obtained in the same manner as in Example 1 were measured using the obtained core material. The handling property was also evaluated.

[Example 8]
With respect to 37.5 parts by mass of fumed silica, 2.8 parts by mass (1.1 parts by mass in terms of solid content) of sodium silicate No. 3 (manufactured by AGC S-Tech Co., Ltd.) was added to 19.1 parts by mass of ion-exchanged water. The binder solution diluted in the part was mixed with a blender. Thereafter, 37.5 parts by mass of fumed silica and M.I. S. 8.3 parts by mass of GEL (manufactured by AGC S-Tech) were added, and silica, magnesia, and calcia fibers (trade name “Superwool (registered trademark) Plus) bulk” as inorganic fibers, D30: 227 μm, D90: 902 μm New Nippon Thermal Ceramics Co., Ltd.) 4.2 parts by mass, graphite (trade name “CP.B”, manufactured by Nippon Graphite Industry Co., Ltd.) 16.7 parts by mass as a radiation suppressing material, and mixed by a blender The material was obtained.
Thereafter, using the obtained core material, the bending strength, the bending strength after temporary fracture, and the thermal conductivity of the vacuum heat insulating material were measured in the same manner as in Example 1.

[Example 9]
As shown in Table 1, a core material was obtained in the same manner as in Example 8 except that 16.7 parts by mass of silicon carbide (trade name “Nisso Random MSU”, manufactured by Taiyo Random Co., Ltd.) was used as the radiation suppressing material. . Thereafter, using the obtained core material, the bending strength, the bending strength after temporary fracture, and the thermal conductivity of the vacuum heat insulating material were measured in the same manner as in Example 1.

[Example 11]
A core material was obtained in the same manner as in Example 9 except that the composition of the core material was changed as shown in Table 1 (no addition of sodium silicate). Then, using the obtained core material, the bending strength of the molded body obtained in the same manner as in Example 1, the bending strength after temporary fracture, and the thermal conductivity of the vacuum heat insulating material were measured.

[Example 12]
Silica, magnesia, calcia fiber (trade name “Superwool (registered trademark) Plus) bulk”, D30: 227 μm, D90: 902 μm, manufactured by Shin Nippon Thermal Ceramics Co., Ltd. with respect to 90 parts by mass of fumed silica. ) 10 parts by mass and 10 parts by mass of graphite (trade name “CP.B”, manufactured by Nippon Graphite Industries Co., Ltd.) as a radiation suppressing material were added and mixed with a blender to obtain a core material.
Thereafter, using the obtained core material, the bending strength, the bending strength after temporary fracture, and the thermal conductivity of the vacuum heat insulating material were measured in the same manner as in Example 1.

[Comparative Examples 1 to 4]
Except that the composition of the core material was changed as shown in Table 1, the bending strength, the bending strength after temporary fracture, and the thermal conductivity of the vacuum heat insulating material were measured in the same manner as in Example 1.

In addition, the symbol in Table 1 has the following meaning.
A-1: Fumed silica (trade name “Aerosil 300”, specific surface area 300 m ² / g, manufactured by Nippon Aerosil Co., Ltd.).
A-2: Porous silica (trade name “MS GEL”, manufactured by AGC S-Itech).
A-3: Graphite (trade name “CP.B”, manufactured by Nippon Graphite Industry Co., Ltd.)
A-4: Silicon carbide (trade name “Nisso Random MSU”, manufactured by Taiyo Random Co., Ltd.).
B-1: Silica magnesia calcia fiber (trade name “Superwool® Bulk”, D30: 227 μm, D90: 902 μm, average fiber diameter: 3 μm, manufactured by Shin Nippon Thermal Ceramics).
B-2: Rock wool (trade name “Mineral Fiber Raw Cotton NM8600”, D30: 253 μm, D90: 668 μm, average fiber diameter: 7 μm (JIS 9504), manufactured by Taiheiyo Materials Co., Ltd.).
B-3: A pulverized product (D30: 75 μm, D90: 629 μm, average fiber diameter: silica, magnesia, calcia fiber (trade name “Superwool (registered trademark) Plus”, manufactured by Nippon Thermal Ceramics)) 3 μm).
D-1: Sodium silicate No. 3 (manufactured by AGC S-Itech).

Table 2 shows the results of measuring the bending strength, the bending strength after temporary fracture, and the thermal conductivity of each example.
In Table 2, “immediate fracture” means that in the three-point bending test, the region where the stress gradually decreases as the strain is increased after the strain where the maximum value of the stress is observed is not observed. It means that the stress becomes zero immediately after the occurrence of the trigger.

As shown in Table 2, the molded products of Examples 1 to 12 had a high bending strength, a sufficiently high bending strength after temporary fracture was observed, and the handling property was good. Further, the vacuum heat insulating materials of Examples 1 to 12 had low heat conductivity and excellent heat insulating performance.
On the other hand, the molded article of Comparative Example 1 having a small proportion of fumed silica could not obtain sufficient bending strength.
Although the cores of Comparative Examples 2 and 4 in which the core material did not contain fibers had sufficient bending strength, immediate fracture occurred and bending strength was not observed after temporary fracture, and handling properties were insufficient. It was.
Although the molded product of Comparative Example 3 having a fiber length D30 of less than 100 μm had sufficient bending strength, immediate fracture occurred and no bending strength was observed after temporary fracture, resulting in poor handling properties. It was enough.

The vacuum heat insulating material obtained by this invention can maintain the outstanding heat insulation characteristic over a long period of time, and can be applied to the place where heat insulation, cold insulation, and heat insulation which require energy saving are required. Specifically, for example, residential and building walls / roofs / floors / piping, solar / heat facilities, etc., constant temperature baths, water heaters, hot water tanks, rice cookers, refrigerators, freezers, cold storage / cold storage tanks, Vending machines, cooler boxes, cold covers, heat insulation and cold insulation fields such as winter clothes, notebook computers, liquid crystal projectors, copiers, batteries, fuel cells and other electrical and electronic equipment, semiconductor manufacturing equipment and other industrial equipment fields, automobiles, It can be applied to mobile fields such as buses, trucks, cold trucks, trains, freight cars, ships, and aircraft.
It should be noted that the entire contents of the specification, claims, abstract and drawings of Japanese Patent Application No. 2014-113179 filed on May 30, 2014 are cited herein as disclosure of the specification of the present invention. Incorporated.

1 Vacuum insulation material 10 Molded body 12 Outer bag

Claims

A molded body in which a core material including fumed silica-containing powder and fibers is molded, is sealed in an outer bag having airtightness under reduced pressure,
The fiber length D30 of the fiber is 100 μm or more, and the fiber length D90 of the fiber is 20 mm or less,
The content ratio of fumed silica in the powder is 70% by mass or more,
A vacuum heat insulating material, wherein a content ratio of the fiber to 2 to 30 parts by mass with respect to 100 parts by mass of the total mass of the powder.
A molded body in which a core material containing fumed silica, a binder, and a fiber is molded is sealed in a hermetic outer bag under reduced pressure,
The fiber length D30 of the fiber is 100 μm or more, and the fiber length D90 of the fiber is 20 mm or less,
The content ratio of fumed silica in the powder is 70% by mass or more,
A vacuum heat insulating material, wherein a content ratio of the fiber to 2 to 30 parts by mass with respect to 100 parts by mass of the total mass of the powder.
The vacuum heat insulating material according to claim 2, wherein a content ratio of the binder to a total mass of 100 parts by mass of the powder is 0.1 to 15 parts by mass.
The vacuum heat insulating material according to any one of claims 1 to 3, wherein the powder further contains one or both of porous silica and a radiation suppressing material.
The vacuum heat insulating material according to claim 4, wherein a content ratio of the porous silica in the powder (100% by mass) is 30% by mass or less.
The vacuum heat insulating material according to claim 4, wherein a content ratio of the radiation suppressing material in the powder (100% by mass) is 30% by mass or less.
The core material comprises a binder with fumed silica binder is applied to the surface, and the ratio of the mass M B of the mass M A and the porous silica of the binder applied prior to the fumed silica contained in the powder ( The vacuum heat insulating material according to any one of claims 4 to 6, wherein M A / M B ) is 70/30 to 100/0.
The vacuum heat insulating material according to any one of claims 1 to 7, wherein the density of the molded body is 0.15 to 0.35 g / cm 3 .
The vacuum heat insulating material according to any one of claims 1 to 8, wherein the fiber is one or both of a resin fiber and an inorganic fiber.
The fibers are alumina fiber, mullite fiber, silica fiber, glass wool, glass fiber, rock wool, slag wool, silicon carbide fiber, carbon fiber, silica-alumina fiber, silica-alumina-magnesia fiber, silica-alumina-zirconia fiber, and The vacuum heat insulating material according to any one of claims 1 to 9, comprising at least one inorganic fiber selected from the group consisting of silica, magnesia, and calcia fibers.
The vacuum heat insulating material according to any one of claims 1 to 10, wherein a degree of vacuum in the outer bag is 1 × 10 3 Pa or less.
The vacuum heat insulating material according to any one of claims 1 to 11, which has a bending strength of 5 kPa or more and a bending strength after temporary fracture of 5 kPa or more.